DESCRIPTION: Musculoskeletal disorders of the extremities (UEMSDs) affect tendons, tendons sheaths, muscles, nerves, bursae, and blood vessels of the hands arms, shoulders, and neck. In 2000, disorders associated with repeated trauma "accounted for 67% of all work-related illness in the United States. Inconsistent associations between physical job stressors and UEMSDs are commonly reported. These inconsistencies are related to imprecise measures of exposure, incomplete control of confounding, poor ascertainment of health outcome, and near exclusive reliance on studies of cross-sectional design. To better estimate effects of work on musculoskeletal health, a prospective epidemiologic study of manufacturing workers is proposed. Approximately 600 study participants will be enrolled over 1.5 years and followed for up to 3 years. At the time of enrolment, musculoskeletal symptoms will be documented and demographic, personal health, work history, and occupational psychosocial stress information will be collected. Information about exposure to physical job stressors will be obtained from a combination of two sources. First, for each study participant, forceful exertions, upper extremity repetition, and upper extremity postures associated with all tasks performed at his/her job will be quantified by observations and direct methods. Second, all study participants will be asked to record in a task log, on a daily basis, the number of hours he/she spent performing each of the specific tasks that are required by his/her job. The physical job stressors for each task will be combined with information from each participant's log of specific tasks performed over time to create a unique time series of exposure information. Any changes to the employee's tasks will be recorded in the task log and will trigger and exposure reassessment. Study participants will also record occurrences and severity of upper extremity symptoms. Those participants with new onset of symptoms that meet a priori criteria will undergo standard clinical examination. Two primary aims will be addressed: 1) the incidence of specific UEMSDs will be estimated among manufacturing workers and 2) multivariate analyses that incorporate time-varying independent variables will be performed to test the hypothesis that incident UEMSDs are associated with physical job stressors after controlling for potential confounding variables.